Typically, fluid actuator cylinders are provided with a wall thickness which is sufficient to withstand the internal operational pressures and a bore of predetermined diameter which is precision machined to permit a piston to smoothly reciprocate therein. During use, the walls of the bore may become worn and pitted, thus presenting a rough surface for the piston and piston seals to slide on. The worn and pitted surfaces may cause severe damage to the piston and seals, resulting in severe leakage of fluid from the cylinder, causing unsafe shutdown of the system in which the actuators are used.
Once the inner walls of the cylinder bore have been pitted or worn and leakage occurs, it is necessary to shut down the system in which the actuator is being used and to replace or repair the worn actuator. Typically, when replacing the defective actuator, it is required to order and await delivery and installation of the new actuator. This is usually a time-consuming process which results in excessive "down time" of the entire system.
Alternately, the entire actuator is removed from the system and repaired by reboring and honing the damaged bore and replacing the piston with an oversized piston. This procedure is costly and time-consuming. Another manner in which the actuator body is typically repaired is by removing the existing piston, reboring the damaged walls of the bore, and installing a liner in the rebored actuator body. The internal diameter of the liner must be sized to accommodate the diameter of the piston to be installed. In most instances, the wall thickness of the liner must be such as to make the internal diameter of the actuator body the same as it was before the reboring process. This process is time-consuming and expensive.
Furthermore, boring very large actuator bodies presents a multitude of other problems. For example, special apparatus must be used in handling very large cylindrical bodies (for example, cylindrical bodies approximately 10 feet long and 3 feet in diameter and having a substantial wall thickness). Such structures are usually very heavy and cumbersome, and boring such structures is virtually impossible in a typical machine shop.
Applicant proposes to eliminate such problems by manufacturing actuator bodies in a modular configuration which eliminates the costly and time-consuming repair or replacement procedures discussed above. To this end, the actuator of the present invention includes a plurality of actuator bodies (or modules) which are secured together in serial relation with a single cylindrical liner common to and mounted in each of the modules. The modules are adapted for assembled relation to achieve the desired length necessary to accommodate the piston stroke. The modules are manufactured with various lengths and bore diameters as well as wall thicknesses.
The material of which the actuator body and liner is made is chosen for the particular application of the actuator assembly. For example, if a lightweight actuator assembly is required, the actuator body may be made of aluminum magnesium or other lightweight material. The liner is chosen to be compatible with the medium which is used in the system.
Aluminum, for example, is very useful in systems which have weight restrictions; however, aluminum liners may not be compatible in an emulsion environment having a high percentage of water. Steel is useful as a liner in general service. Bronze may be used for general water service conditions. Stainless steel has application in corrosive environments, and electrodeless nickel is applicable in clean water environments. Plastic liners or plastic-coated liners may be useful in various environments.
Some prior art patents exist which disclose the use of sleeves in internal combustion engines. U.S. Pat. No. 2,324,547, issued to Wagner on Jul. 20, 1943, discloses a liner for a cylinder of an internal combustion engine and method of lining the engine cylinder. U.S. Pat. No. 1,321,792, issued to Jackson on Nov. 11, 1919, also discloses a sleeve for cylinders of an internal combustion engine. The sleeve further includes circumferential passages or grooves on its external surface for circulating coolant between the sleeve and the internal surface of the cylinder bore. U.S. Pat. No. 4,370,788, issued to Baker on Feb. 1, 1983, discloses a method of aligning a cylindrical bore of an internal combustion engine and includes the provision of a strip of material having free ends and which is formed into a hoop which is subjected to hoop stress.
U.S. Pat. No. 3,094,773, issued to Bukoff on Jul. 25, 1963, is directed to a process for installing sleeves in the cylinder bore of a fluid motor such as found in the aircraft wheel and brake art and includes machining the bore at one end with a recess to receive a shoulder which has been formed on an end of the liner.
U.S. Pat. No. 2,412,587, issued to Larson on Dec. 17, 1946, is directed to hydraulic brake systems on motor vehicles and particularly to the master and wheel cylinders of the vehicles. The patent is specifically directed to means for removably holding the sleeve in place in the cylinder bore.
None of the above patents are directed to a modular fluid actuator wherein the actuator body is comprised of a plurality of body members having a bore of predetermined diameter therein and wherein the modular body members are secured in abutting, serial relation, and a single common liner is carried in the bores of the body members.